Presbyopia contact lenses that are applied to presbyopic eyes to compensate for deteriorated vision accommodation ability are known from the past. A presbyopia contact lens has a plurality of regions provided with different lens powers set within the optical region of a single contact lens. Specifically, the optical region of the presbyopia contact lens has a near region with a suitable lens power set for when doing nearby observation and a distance region with a suitable lens power set for when doing far distance observation. Furthermore, when necessary, an intermediate region or a transition region, wherein a lens power that is adjusted to intermediate distance observation is set, is provided therefor.
Also, by selectively or simultaneously using the near region and the distance region, eyesight correction is performed according to the needed distance. For example, as an alternative vision type presbyopia contact lens used for which the near region and the distance region are used selectively, there is the item noted in Japanese Unexamined Patent Publication No. JP-A-63-95415 (Patent Document 1). For the item, it is possible to obtain the necessary visual acuity by moving the visual axis to have regions of different lens powers selectively used. Also, as a simultaneous vision type presbyopia contact lens for which the near region and the distance region are used simultaneously, there is the item noted in Japanese Unexamined Patent Publication No. JP-A-59-208524 (Patent Document 2). For the item, by simultaneously observing regions of different lens powers and having the brain make a judgment, the necessary images are selected and recognized, and it is possible obtain the necessary visual acuity.
However, in the case of either the alternative vision type or the simultaneous vision type, the prior presbyopia contact lenses, as with Patent Document 1, were bifocal types for which fixed lens powers were set for both the near region and the distance region. In addition to this, in recent years, for at least one of the near region and the distance region, progressive type (progressive multifocal type) presbyopia contact lenses for which non-step changing lens powers were set were provided (see Patent Document 2).
This progressive type presbyopia contact lens is able to give an optical focal point to a continuously changing seeing distance, so compared to the bifocal type presbyopia contact lens, we can expect provision of natural vision to the user by compensating for the vision accommodation ability of the eye optical system in non-step form. Because of that, for both presbyopia contact lens users and prescribers, many are selecting progressive type presbyopia contact lenses because they anticipate having the eye focus to continuously match as the seeing distance changes to see items of any distance well.
However, according to an investigation by the inventors of the present invention, when progressive type presbyopia contact lenses were actually worn, it became clear that there were many cases of not being satisfied with vision. In fact, suitability of presbyopia contact lenses that can provide satisfactory vision depends on the individual, and in the past, it was difficult to select the optimal presbyopia contact lens for each user.
Specifically, it is also conceivable to prepare in advance many types of presbyopia contact lens with differing lens power, additional diopter power, power profile and the like so as to select the optimal item by trying them on each individual and comparing. However, with that kind of handling method, not only does the seller have to have many types of contact lenses available in advance, but it is also necessary for the user to repeatedly put on and take off the contact lenses many times. This is a forced time and physical burden on both the user and prescriber, and is not practical.